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Cubsfan
01-03-2008, 06:17 PM
(CH_sub3)sub3

Not sure how to make this thing do subscripts but the 3s are subscripts. I'm sure there is a way to just punch this into google or something to puke it out but I can't figure that out. I need to use a name for this gas in addition to the chemical shorthand. I think it's Trimethylane. Does that sound right? Or is it 3-Trimethylane?

(In case you are wondering if this is homework it's not. I'm trying to describe the process of creating TMG (Trimethylgallium) by passing gas through a bubbler and I need a word for the gas so I can say it out loud)

GameHat
01-03-2008, 06:37 PM
As you've written it (CH3)3 this is a nonexistant molecule

Carbon is tetravalent so there's no way to get 3 methyl groups to bond together unless one of them loses a hydrogen

CH3CH2CH3 would be propane

Carbon does not form 3 membered rings (too much stress). IIRC, 4 membered carbon rings are EXCEEDINGLY rare (lab only). 5 membered carbon rings OK.

As for gallium? Sorry, don't know much about that.

GameHat
01-03-2008, 06:39 PM
As you've written it (CH3)3 this is a nonexistant molecule

Carbon is tetravalent so there's no way to get 3 methyl groups to bond together unless one of them loses a hydrogen

CH3CH2CH3 would be propane

Carbon does not form 3 membered rings (too much stress). IIRC, 4 membered carbon rings are EXCEEDINGLY rare (lab only). 5 membered carbon rings OK.

As for gallium? Sorry, don't know much about that.

Also, C(CH3)3 would be 2-methyl propane or Isobutane

GameHat
01-03-2008, 06:41 PM
THIS (http://webbook.nist.gov/cgi/cbook.cgi?ID=C28933848&Units=SI) is the closest I can find and it's not a stable compound but a radical

WarmNPrickly
01-03-2008, 07:02 PM
Your synthesis is no doubt lacking something. As everyone else has suggested, (CH3)3 is a non-existent compound. I have banged my head for the past ten minutes, trying to come up with what you actually mean, but the fact is that your synthesis is just plain wrong.

Theoretically, you could mix CH3MgBr (methyl gingard) with Gallium trichloride to get trimethyl gallium. That is the closest facsimile I could come up with to what you actually mean. Technically, this might be described as the reaction between 3•CH3– and Ga3+, but I dont think that CH3MgBr is a gas.

Squink
01-03-2008, 07:06 PM
Carbon does not form 3 membered rings (too much stress).
Sure it does: Cyclopropane (http://en.wikipedia.org/wiki/Cyclopropane).

WarmNPrickly
01-03-2008, 07:14 PM
Squink is completely right on this. A large part of my disertation is dedicated to the synthesis of cyclopropenes, which are worlds less stable than cyclopropanes, yet they stuck around long enough to stick in the freezer for a few days. They were even stable for a few months depending oon the derivative.

Cubsfan
01-03-2008, 07:49 PM
(CH3)3 Ga + (NH)3 --> GaN + 3CH4

That is basic chemical reaction that is used to grow GaN wafers. The first compound is called Trimethylgallium or TMG for short. I (apparently incorrectly) assumed that TMG was created by bubbling (CH3)3 through liquid/vaporized gallium.

I guess since the (CH3)3 isn't real I'm trying to figure out how they make TMG. This is for a written and oral explanation of how they create GaN wafers using the MOCVD process. The creation of the TMG is proving to be a little tricky for me to find in my locally accessible literature.

BTW, I am 100% confident in the above reaction equation.

http://en.wikipedia.org/wiki/Trimethylgallium

Cubsfan
01-03-2008, 07:59 PM
Hmmm...I've been doing alot of web searching since I got home and can't find ANYTHING on how TMG is created. Everything I can find is regarding the above equation and the creation of GaN via MOCVD with pre existing TMG. This is tricky.

WarmNPrickly
01-03-2008, 08:17 PM
Your reaction: ((CH3[/b])[sub]3Ga + NH3 ---> GaN + CH4 almost definitely requires energy, because I strongly suspect that ((CH3)3GaNH3 is a stable adduct. Nevertheless, it clearly works as you state.

From what I have found (http://www.patentstorm.us/patents/6495707-description.html), trimethyl gallium is indeed synthesized from the grignard reacion I suggested. In place of CH3MgBr, one might also use CH3Li, (CH3)3Al, or (CH3)4AlLi (I made that last one up, but I got a good feeling it works.) In any case, they will be reacted with GaX3 where X represents a labile negative ion such as Cl, Br, I?, OTf, or OTs.

In any case, under ordinary conditions, you are not bubbling a gas, through a gallium solution. I wonder if there might be a procedure simliar to what you describe involoving diazomethane (gas), but another hydrogen is needed.

WarmNPrickly
01-03-2008, 09:10 PM
I am almost certain now that the compound you are refering to is (CH3)3Al (http://en.wikipedia.org/wiki/Trimethylaluminium). Since it is a liquid at 15˚C and a gas at 125˚C, it is not unreasonable to deal with it as a gas. The semiconductor industry is a long way from synthetic organic, so be advised on my expertise.

ETA: It would be reacting with GaCl3

GameHat
01-03-2008, 09:32 PM
Sure it does: Cyclopropane (http://en.wikipedia.org/wiki/Cyclopropane).

I stand corrected

Cubsfan
01-03-2008, 10:36 PM
I am almost certain now that the compound you are refering to is (CH3)3Al (http://en.wikipedia.org/wiki/Trimethylaluminium). Since it is a liquid at 15˚C and a gas at 125˚C, it is not unreasonable to deal with it as a gas. The semiconductor industry is a long way from synthetic organic, so be advised on my expertise.

ETA: It would be reacting with GaCl3

Well, it's both actually. Trimethylaluminum (TMA) is used to make AlN and TMG is used to make GaN, noth reacting with ammonia to do so, but both TMG and TMA are used together to grow AlGaN with the ratio of TMA to TMG being the final mole fraction of aluminum.

I've never actually seen a bubbler and am not sure how they work but the process sends a gas thru the bubbler (hydrogen maybe?) which carries the TMG or TMA to the reaction chamber where it is combined with ammoina to grow GaN or AlN. I was hoping there were more details on how they make TMG.

Thanks for all your help though. Very infomative!

WarmNPrickly
01-04-2008, 07:59 AM
The point I was making, was that TMA can be used to synthesize TMG from GaCl3. If you simply tack on an aluminum to your original formula, (CH3)3, you get TMA. Bubbling TMA through a solution of GaCl3 will make TMG. From my previous link:

Trimethylgallium is normally prepared by means of such a batch process using gallium trichloride and a suitable alkylating agent such as a Grignard reagent, Lithium reagent or trialkylaluminium.

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